Boiler control mechanism



May 15, 1934. A. L. cox

BOILER CONTROL MECHANISM Filed July 11, 193s f//mf77/iarfax /yw Patented May 15, 1934 UNITED STATES PATENT? OFFICE More particularly the invention relates to a mechanism for controlling the draft on a boiler so as to hold the fire if the water temperature or steam pressure falls and there is a tendency for the re to burn out.

Generally the temperature or pressure operated draft control of the boiler functions to increase the draft as the steam pressure or temperature drops so as to increase the fire and build up the heat of the boiler. If however, there is insuflicient fuel in the furnace to bring up the heat of the boiler, the draft remains at its increased value and before long, if the attendant is away, the fire will burn out.

It is the general object of the invention to provide a new and improved control mechanism for modifying the draft in case the fire fails to respond to the demand for heat, thereby holding the fire for a relatively long period of time during which the attendant has ample opportunity to return.

Another object is to provide such a control mechanism which may be set manually by an attendant and which will thereafter operate to again decrease the draft should the steam pressure continue to drop after the draft has been increased.

Another object is to provide such a mechanism in the form of an attachment which may be readily installed on existing boilers, and which is simple in construction and can be manufactured at a low cost.

Further objects will become readily apparent from the following detailed description, taken in connection with the accompanying drawing, in which:

Fig. 1 is a front elevation of a boiler with a preferred form of the invention installed thereon.

Fig. 2 is a fragmentary side elevation.

Fig. 3 is a vertical section through the control mechanism.

Fig. 4 is a fragmentary section of a modified form of the invention.

Although I have illustrated in the drawing and shall herein describe in detail a preferred embodiment of the invention, together with a modied form thereof, I do not intend to limit the invention to the specific forms and arrangements shown, but aim to cover all modifications and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

Referring to the drawing, a preferred form of the invention is installed on a boiler 10 having a pivotally mounted draft door 11, a check draft door 12, and a pressure operated control device 13 for operating said doors. 'I'he control device 13 may be of the expansible bellows type and includes a member 14 which is raised automatically as the steam pressure increases, and which is lowered as the steam pressure decreases. A lever 15 is adjustable longitudinally in a pivotally mounted member 16 and carries an adjustable weight 17. The member 14 engages under the member 16 so as to operate the lever. At its 6 5 right-hand end the lever 15 is connected by means =of a chain 18 to the draft door 11, and by means of a second chain 19 to' the check draft door 12. The arrangement is such that when the draft door 11 is open the check door 12 is closed, and 7T()y vice versa, a certain amount of slack, however, being preferably provided in the chains so that the check door 12 will close prior to the opening of the draft door, and correspondingly the draft door may be closed prior to the opening of the 'Z5 check door.

In the normal operation of the control mechanism already described, if the pressure drops, the member 14 will descend due to the action of the weight 17, with the result that the lever 15 turns in a counterclockwise direction, from the dotted line position to the solid line position (Fig. 1), thereby closing the check door 12 and opening the draft door 11. The draft door will remain open (and the check door closed) until the fire picks up and generates steam sumcient to raise the pressure and cause the operating member 14 to pivot the lever 15 and close the draft door. If, however, the fire is in such a condition that the steam pressure does not rise suiiiciently to close the draft door, the draft would remain open and before long the fire would burn out. The present invention provides a control mechanism operable .to close the draft door if the steam pressure continues to drop when the draft is open, due to the failure of the fire to generate additional steam.

rI'he control mechanism in the form illustrated herein comprises generally means for operating the lever 15 and, through the chains 18 and 19, the draft and check doors 11 and 12, to close the draft door and open the check door. To accomplish this a weighted device 25 is movably mounted on a supporting bracket 26. The weighted device 25 is shown in the form of a piston slidably mounted in a cylinder 27 held in a vertical position by the bracket 26. A rod 28 is connected to the piston 25 and carries means in the form of an adjustable arm 29 having a depending bifurcated portion 30 straddling the lever 15, for operating the lever. The weighted device is arranged to be elevated manually to the position illustrated in Fig. 3, in which position it is held by means of a latch device 31 which is pivotally mounted on a closure 32 for the upper end of the cylinder and has a hooked portion 33 arranged to engage a collar 34 formed by an annular groove 35 adjacent the upper end of the member 25. Means for operating the-latch device to release the weighted piston is herein shown as comprising an arm 36 which is pivotally connected to the latch device 3l by a vertical pin 36', a spring 36 being provided for normally holding the arm 36 in its extended position. This arm extends o-Ver the lever 15 so as to be operated by the lever when the steam pressure reaches a predetermined minimum, indicative that the fire has failed to generate sufcient steam to continue the boiler in operation. Thus when the steam pressure falls, the draft door 1l is opened by means of lever 15 and continues to open farther if the pressure continues to fall. Upon failure of the rire to generate sufcient steam tor increase the pressure, the lever 15 continues its counterclockwise movement (Fig. l) until it engages the latch operating means 36, whereupon the weighted device 25 is released and descends. During such descent a shoulder 37 on the arm 29 engages the lever 15 and pivots the lever in a clockwise direction (Fig. 1) so as to close the: draft `door and open the check door, thereby holding the fire.

. Preferably means is provided for cushioning the descent of the weighted ldevice so as to prevent unnecessary j'ar and noise. As illustrated in'Fi'g. 3, the piston 25 may be somewhat loose fitting in the cylinder 27 and the lower portion of the cylinder filled with a iiuid 38, such as oil. If desired 'a coiled spring 39 may be positioned in the lower end of the cylinder and used either with or without a fluid in the cylinder. As illustrated in Fig. 4, a washer 40 is secured to the lower end of the piston so as to slow up the descent of the piston while at the same time permitting the piston to be raised manually and quickly. WithV such a construction the air in the lower portion of the cylinder is relied on to cushion the descent, a restricted exhaust port 41 being provided through the piston. The rate of descent may be regulated by means of a valve device 42 for controlling the port 41. When the weighted device is in the form of a piston the cylinder cooperates therewith to form in effect a dash pot for cushioning the descent.

It is believed readily apparent that the invention provides a simple and effective means for closing the draft door should the fire fail to respond and generate steam. The weighted device 25 illustrated in the exemplary embodiment of the invention serves as a power means for closing the draft, contrary to the normal operation of the lever 15 due to the weight 17. The invention may be provided in various forms of attachments which may be installed on existing boilers for the purpose of operating draft control mechanisms now in use.

I claim as my invention:

1. In combination with a boiler having a draft door and pressure responsive means operable to open said door when the pressure drops below a first predetermined value, control mechanism operable to close the draft door as the pressure drops below a second predetermined value Idue to the failure of the fire to generate additional steam.

2. In combination with a boiler having a draft door and means including a lever operable to open said door when the pressure drops below a rst predetermined value, power means operable to close the draft door as the pressure drops below a second predetermined value due to the failure of the fire to generate additional steam, and means operable by said lever for initiating operation of said power means.

3. In combination with a boiler having a draft door and pressure responsive means operable to open said door when the pressure drops below a Vfirst predetermined value, control mechanism operable Ato close the draft door as the pressure drops below a second predetermined value due tothe failure of the re to generate additional steam, comprising a weighted device adapted to be set manuallyat an elevated position.

4. A control mechanism of the character described for automatically closing the draft door of a boiler should the steam pressure fall below a predetermined valueY comprising a supporting bracket, a vertical cylinder carried on said bracket, a weighted piston in said cylinder, a piston rod connected to said piston, means connecting said rod to operate the draft door, latch means for releasably holding said weighted piston in an elevated position, means for operating said latch means when the pressure drops below said predetermined value, and means for cushioning the descent of the piston.

5. A control mechanism of the character described for closing the draft door of a boiler should the steam pressure fall below a predetermined value comprising a supporting bracket, a vertical cylinder carried on said bracket, a weighted piston in said cylinder, means connecting said piston to operate the draft door, latch means for releasably holding said weighted piston in an elevated position, means for tripping said latch means when the pressure falls below said value, and means for. cushioning the descent of the weighted piston when released.

6. A control ymechanism of the character described for automatically closing the draft door of a boiler should the steam pressure fall below a predetermined value comprising a support means, a weighted member movable vertically on said means, means connecting said member to close the draft door during descent'of ther member, latch means for releasably holding said weighted member in an elevated position, and means for releasing said latch means when the pressure falls below said value.

'7. In combination with a boiler having a draft door and pressure responsive means including a lever operable to open said door when the pressure drops below a first predetermined value, control mechanism operable to close the draft door as the pressure drops below a second pre' determined value due to the failure of the re to generate additional steam comprising a support, a weighted member movably mounted on said support, means for releasably latching said weighted member in an elevated position on said support including a trip device operable by said lever, means on said weighted device for depressing the lever to close the door when the device is released, and a dash pot mechanism for cushioning the descent of said weighted device. i

8. In combination with a boiler having a draft door and pressure responsive means including a lever operable to open said door when the pressure drops below a first predetermined value, control mechanism operable to close the draft door i.

as the p essure drops below a second predetermined value due to the failure of the fire to generate additional steam comprising a support, a weighted member movably mounted on said support, means for releasably latching said weighted member in an elevated position including a trip device operable by said lever, and means on said weighted member for depressing the lever to close the door when the device is released.

9. In combination with a boiler having a draft door and pressure responsive means including a lever operable to open said door when the pressure drops below a first predetermined value, control mechanism operable to close the draft door as the pressure drops below a second predetermined value due to the failure of the fire to generate additional steam comprising a support, a Weighted member movably mounted on said support, means for reieasabiy latching said weighted member in an elevated position including a trip device operable by said lever, means on said weighted member for depressing the lever to close the door when the member is released, and means for cushioning the des-cent of said weighted member.

l0. in combination with a boiler having draft regulating means and pressure responsive means operable to control the draft regulating means to increase the draft when the pressure drops below a first predetermined value, control mechanism operable to cause the draft regulating means to again decrease the draft when the pressure drops below a second predetermined value due to the failure of the fire in the boiler to generate additional steam.

il. In combination with a boiler having draft regulating means, control mechanism operable to cause the draft regulating means to increase the draft when the temperature of the boiler falls below a first predetermined value and to again decrease the draft when the temperature falls below a second predetermined value due to the failure of the re in the boiler to raise the temperature thereof.

12. In combination with a heat generating source having draft regulating means, control mechanism operable to cause the draft regulating means to increase the draft when the temperature to which the mechanism is exposed falls below a rst predetermined value and to again decrease the draft when the temperature falls below a second predetermined Value.

13. In combination with a boiler having draft controlling means comprising a draft door and a check draft, and pressure responsive means operable to actuate said draft means to increase the draft when the pressure falls below a first predetermined value, control mechanism operable to actuate said draft means to decrease the draft when the pressure drops below a second predetermined value due to failure of the re in the boiler to generate additional steam.

14. In combination with a boiler having draft regulating means, means responsive to the heat condition of the boiler operating to control said regulating means to decrease the draft when the boiler is heated above a rst predetermined value and to increase the .draft when the heat of the boiler falls below the predetermined value, and releasable means operating when the heat of the boiler falls below a second predetermined value to again decrease the draft, said releasable means retaining the draft decreased until manually reset.

l5. In combination with a boiler having a draft regulating means and pressure responsive means including a lever operable to cause the regulating means to increase the draft when the pressure falls below a first predetermined value, control mechanism comprising a support, a weighted member movable vertically on said support, and in its descent actuating said lever to cause the regulating means to again decrease the draft, and latch means for releasably holding said weighted member in elevated position, said pressure responsive means operating to release said latch means when the pressure falls below a second predetermined value.

ARTHUR L. COX. 

